1. Field of the Disclosure
The present invention is generally related to power converters, and more specifically, to boosting power converter controller supplies.
2. Background
A power converter controller typically receives power for its internal blocks from a supply terminal. In some instances, this supply terminal may sometimes also be referred to as a bypass (BP) terminal, or sometimes as a VDD supply. A large group of power converters, such as for example flyback converters, include magnetic isolation or transformer with two or more windings (sometimes referred to as the energy transfer element comprising two or more coupled inductors). In power converters with transformer the voltage to the bypass terminal is provided during normal operation after startup through an extra auxiliary winding (sometimes referred to as a third winding or a second of the coupled inductors) on the transformer core. Thus an auxiliary winding sometimes may also be referred to as a supply or bypass winding. The ac induced voltage on the auxiliary winding is rectified and filtered on a supply terminal capacitor coupled to the bypass terminal and the auxiliary winding to generate a dc supply voltage on the bypass terminal.
At startup, before the voltage on the supply terminal capacitor coupled to the bypass terminal and the auxiliary winding is charged to a regulated voltage, supply voltage may be provided from some external source, such as the input dc bus, to the supply terminal capacitor. The voltage on the supply terminal capacitor coupled to bypass terminal and the auxiliary winding may then be regulated after startup during normal operation though the power converter controller and/or shunt regulator after the supply terminal capacitor is charged. A slow charge up of the supply voltage on the supply terminal capacitor during startup delays normal operation of the power converter controller until after the startup operation is complete.
Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.